A Janus porous sphere with a coral-like microstructure is prepared by stepwise dealloying a metallic alloy sphere and sequential modification (for example, using silanes and polymers). Nanoscale coral-like microstructure of the internal skeleton gives remarkable capillary force, thus accelerating the mass transportation. Starting from the outer layer of the sphere, stepwise dealloying can achieve different layers inwardly, thus introducing different composition and performance. As an example, poly(ethylene glycol)-poly(N-isopropylacrylamide) (PEG-PNIPAM)- and poly(ethylene glycol)-poly(N,N-diethylamino-2-ethylmethacrylate) (PEG-PDEAEMA)-responsive Janus porous spheres can quickly capture oil by simply changing temperature or pH. Similarly, release is also triggered.
Keywords: Janus; capillary force; coral microstructure; dealloying; porous; responsive.